Application

Fluidisation

Powder is supposed to flow like water in the container; correctly fluidised powder should appear like simmering water.  There are various tests for powder coating fluidity, most notably the 'Sames Test' (AFNOR) which gives a R value to a powder coating.

Poor fluidisation

Poor fluidisation is apparent as a slow and non-continuous transportation of the powder coating from the fluid container to the guns.  Additionally, poorly fluidising powder will create volcano-like hills or rat-holes on the surface of the ‘fluid’ powder.  When spraying, the powder cloud is inconsistent.

  • Potential Cause

    Fluidising air pressure is too low.

  • Solution

    Adjust the pressure to achieve the correct fluidity, look for the fluidised powder surface to appear to gently simmer.

  • Potential Cause

    Compact or damp powder

  • Solution

    Manually loosen powder in hopper, if humidity is the cause, leaving the box open to the atmosphere will normally correct the problem.  In some circumstances it may be necessary to add a small amount of dry-flow aid to improve the coating’s fluidity.  Check compressed air for moisture quality, it is vital that the air is clean and dry.

  • Potential Cause

    Fluidising plate clogged / defective

  • Solution

    Clean or replace plate

  • Potential Cause

    Too many 'fines' in the powder coating

  • Solution

    Decrease amount of reclaim to hopper.  Check ratio of virgin powder

Over fluidising

Powder dusting out of hopper and fluidised powder appears to be 'boiling'.

  • Potential Cause

    Fluidising air pressure is too high.

  • Solution

    Reduce air pressure to fluid bed; properly fluidised powder will appear to gently simmer, not boil.

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